Expression of specific carbohydrates by transfection with carbohydrate modifying enzymes

The glycomics of glycan glucuronylation in Drosophila melanogaster

As glycan characterization methods increase in sensitivity, new opportunities arise to undertake glycomic analyses on limiting amounts of material. Developing systems present special challenges since the amount of available tissue can restrict deep glycan characterization. We have optimized mass spectrometric methods with the goal of obtaining full glycan profiles from small amounts of tissue derived from organisms of particular interest. A major target of our efforts has been the Drosophila embryo, allowing us to leverage the tools already developed in this organism to meld glycomics, genomics, and molecular genetics. Our analysis of the N-linked, O-linked (non-GAG), and glycosphingolipid (GSL) glycans of the Drosophila embryo have identified expected and unexpected glycan structures. We have verified previous findings regarding the predominance of high-Man and pauci-Man N-linked glycans, but have also detected minor families of sialylated and glucuronylated N-linked structures. Glucuronic acid (GlcA) also presents itself as an abundant modification of O-linked and GSL glycans. We describe critical advancements in our methodology and present the broad range of contexts in which GlcA is found in the Drosophila embryo.

Use of conventional and -omics based methods for health claims of dietary antioxidants: a critical overview

This article describes the principles and limitations of methods used to investigate reactive oxygen species (ROS) protective properties of dietary constituents and is aimed at providing a better understanding of the requirements for science based health claims of antioxidant (AO) effects of foods. A number of currently used biochemical measurements aimed of determining the total antioxidant capacity and oxidised lipids and proteins are carried out under unphysiological conditions and are prone to artefact formation. Probably the most reliable approaches are measurements of isoprostanes as a parameter of lipid peroxidation and determination of oxidative DNA damage. Also the design of the experimental models has a strong impact on the reliability of AO studies: the common strategy is the identification of AO by in vitro screening with cell lines. This approach is based on the assumption that protection towards ROS is due to scavenging, but recent findings indicate that activation of transcription factors which regulate genes involved in antioxidant defence plays a key role in the mode of action of AO. These processes are not adequately represented in cell lines. Another shortcoming of in vitro experiments is that AO are metabolised in vivo and that most cell lines are lacking enzymes which catalyse these reactions. Compounds with large molecular configurations (chlorophylls, anthocyans and polyphenolics) are potent AO in vitro, but weak or no effects were observed in animal/human studies with realistic doses as they are poorly absorbed. The development of -omics approaches will improve the scientific basis for health claims. The evaluation of results from microarray and proteomics studies shows that it is not possible to establish a general signature of alterations of transcription and protein patterns by AO. However, it was shown that alterations of gene expression and protein levels caused by experimentally induced oxidative stress and ROS related diseases can be normalised by dietary AO.

The N-glycolyl form of mouse sialyl Lewis X is recognized by selectins but not by HECA-452 and FH6 antibodies that were raised against human cells

E-, P- and L-selectins critically function in lymphocyte recirculation and recruiting leukocytes to inflammatory sites. MECA-79 antibody inhibits L-selectin-mediated lymphocyte adhesion in several species and does not require sialic acid in its epitope. Many other antibodies, however, recognize human selectin ligands expressing N-acetylneuraminic acid but not mouse selectin ligands expressing N-glycolylneuraminic acid, suggesting that difference in sialic acid in sialyl Lewis X leads to differential reactivity. We found that HECA-452 and FH6 monoclonal antibodies bind Chinese hamster ovary (CHO) cells expressing N-acetylneuraminyl Lewis X oligosaccharide but not its N-glycolyl form. Moreover, synthetic N-acetylneuraminyl Lewis X oligosaccharide but not its N-glycolyl oligosaccharide inhibited HECA-452 and FH6 binding. By contrast, E-, P- and L-selectin bound to CHO cells regardless of whether they express N-acetyl or N-glycolyl form of sialyl Lewis X, showing that selectins have a broader recognition capacity than HECA-452 and FH-6 anti-sialyl Lewis x antibodies.